It is conventionally common that when a projection display apparatus performs a projection operation, it is placed at a stable location due to restrictions, such as power supply of a light emitting means (light source).
Recently, compact light sources are rapidly spreading, which excel in efficiency, output, power consumption, etc. (for example, a light emitting diode (LED) and a semiconductor laser which can be lighted by a compact power source, such as a lithium secondary battery). Therefore, combined with the commercialization of such compact light sources, ultra-compact projection display apparatuses which can perform projection while being carried are being proposed (see Patent Document 1 for example).
In accordance with a mobile phone described in Patent Document 1, the mobile phone incorporates a projection device which can receive map information through an antenna so as to project the map information as a projected image on a flat surface that is a projection surface (wall, etc.).
Typical examples of electrical apparatuses used while being carried are video cameras and digital cameras. Some of these video cameras and digital cameras have a hand movement preventing function which corrects a recorded image distortion caused due to a hand movement. A technology of detecting the swinging of a camera by an angular velocity sensor attached to a video camera main body and correcting the hand movement based on this detection result has already been developed (see Patent Document 2 for example).
One example of the angular velocity sensor is a quartz crystal tuning fork angular velocity sensor. By applying a voltage to a tuning fork shaped quartz crystal, the quartz crystal tuning fork angular velocity sensor oscillates in one direction due to its piezoelectricity.
When an angular velocity is added to the quartz crystal tuning fork angular velocity sensor in this state, Coriolis force acts, a voltage is generated in a direction orthogonal to the applied voltage, and thus the angular velocity can be detected. Therefore, by attaching the quartz crystal tuning fork angular velocity sensor to the camera main body, the state of the hand movement (angular velocity) of the camera can be detected easily. As a result, feedback control (suitably rotating a lens of a camera optical lens system) can be performed based on a swinging correcting signal corresponding to an output signal of the quartz crystal tuning fork angular velocity sensor, and therefore, the recorded image distortion caused due to the hand movement of the camera can be corrected.
Patent Document 1: Japanese Unexamined Patent Publication 2002-261889
Patent Document 2: Japanese Unexamined Patent Publication 60-143330